Before choosing a table lamp, let’s first understand our country’s national standards. On the market, any table lamp that dares to claim "eye protection", "comfort", and "study and work use" should have its performance parameters within the scope of the GB/T 9473 standard specification. It must meet the performance requirements stipulated by the standard, otherwise it is false propaganda.

The performance parameters mentioned here mainly include the uniformity of illuminance intensity, shading, color temperature and blue light hazard of the retina. If you want to know more about the specific content of the specification, you can check the relevant information given below. Next, we will understand from these dimensions, what kind of quality a qualified eye protection table lamp has.

Ps: (National Standard GB/T 9473-2017 "Performance Requirements for Reading and Writing Table Lamps" was formulated by the National Shanghai Institute of Product Quality Supervision and Inspection. It was approved for publication on September 30, 2017 and officially implemented on April 1, 2018. Replace the original GB/T 9473-2008 standard.)

1. Illumination intensity and uniformity
We must first figure out what is illuminance? Sufficient illuminance can ensure that the eyes have a good degree of recognition of the target. The simple understanding is that the brightness must be appropriate, not too dark or too bright, so it seems that it is quite difficult to accurately determine this degree! Then you might as well take the brightness of the natural light source around 10 o'clock in the morning as a reference.

In any case, it is enough to ensure that our eyes see things easily under this light source. The so-called effortlessness means that the eyes can see clearly without large-scale adjustment of pupil muscles.

Camera friends should understand that when the light is dim, to ensure correct exposure, you need to increase the aperture to increase the amount of light in the case of the same time. On the contrary, reduce the aperture to reduce the amount of light. Eyes are similar to cameras. They rely on adjusting the size of their pupils to achieve "adjustment of the aperture" on the camera to increase or decrease the amount of light entering.

Of course, it is not enough to satisfy the requirement of sufficient light, but also to consider whether the light is uniform. If the light is uneven, it will cause the eyes to constantly adjust themselves in different light and dark areas, which will quickly cause fatigue and cause eye discomfort in a short time. Therefore, illuminance intensity and uniformity are two important indicators of constant visual comfort. If you want more specific standards and regulations, please refer to the following four points:

In the central area and edge area of ​​reading and writing, the illuminance and uniformity of the lamps must be at least Class A, preferably Class AA;

A-level illumination requires at least 300lx in the central area and 150lx at the edge;

AA-level illuminance requires at least 500lx in the central area and 250lx at the edge;

The requirements for uniformity of illuminance (the ratio of the maximum value to the minimum value) of A-level and AA-level are not more than 3.

(Lx is the international unit of illuminance, which is the abbreviation of lux in English, and its physical meaning is the luminous flux irradiated on a unit area)

2. Shading
The shading can be understood only literally. For example, in the process of using a desk lamp, if we get tired in a posture, stretch our waist, raise our head and move our neck, our eyes will inevitably touch the outer lampshade of the lamp. If the lampshade is opaque, the brightness contrast will be produced. It will make our eyes uncomfortable; if the light transmittance of the lampshade is too good, its brightness is much greater than the brightness of the paper, and it will also feel uncomfortable to the eyes. Therefore, the right light transmission can make our eyes more comfortable.

Therefore, the lampshade of a comfortable desk lamp must have a certain degree of shading, and when we are in a working sitting position, the surface brightness of the light-emitting part that can be seen up to the head cannot be higher than 2000cd per square meter, which is considered a qualified protection. The light-shielding property of the table lamp.

(Cd is the international unit of luminous intensity, which is the abbreviation of candela in English, called candela, and its physical meaning is the size of the luminous flux transmitted by the light source in a solid angle in a certain direction)

Three, color temperature
Regarding color temperature, I think everyone is more familiar with "warm light" and "cold light". The color temperature of the light source determines the color of the light and also brings us different feelings. When the color temperature is less than 3000K, the light color is white and red. Warm feeling; when the color temperature is between 3000K and 5000K, the light color is white, which makes people feel natural and comfortable; when the color temperature is >5000K, the light color is white with blue, giving people a refreshing feeling.

(K is the international unit of color temperature, which is the abbreviation of English Kelvins, called Kelvin, and its physical meaning is that the spectral component of the black body when heated is the color temperature at the current temperature)

However, in actual use, the color temperature should not exceed 4000K. Especially at night use, too high color temperature will bring more blue light spectrum, we will talk about the specific harm of blue light in the next section. It is stipulated in the relevant standards that if the color temperature of the LED light source used is higher than 4000K, then the product manual must indicate the reminder to avoid night use. If there is a color temperature adjustment function, it should also give a clear reminder to inform the user that it is at night The color temperature should be adjusted below 4000K for use.